This study examined the effect of character sample density on legibility. As the spatial frequency component important for character recognition is said to be 1 to 3 cycles/letter (cpl), six dots in each direction should be sufficient to represent a character; however, some studies have reported that high-density characters are more legible. Considering that these seemingly contradictory findings could be compatible, we analyzed the frequency component of the character stimulus with adjusted sample density and found that the component content of 1 to 3 cpl increased in the high-density character. In the following three psychophysical experiments, high sample density characters tended to have lower contrast thresholds, both for normal and low vision. Furthermore, the contrast threshold with characters of each sample density was predicted from the amplitude of the 1 to 3 cpl component. Thus, while increasing the sample density improves legibility, adding a high frequency is not important in itself. The findings suggest that enhancing the frequency components important for recognizing characters by adding the high-frequency component contributes to making characters more legible.

这项研究检验了字符样本密度对易读性的影响。由于对字符识别很重要的空间频率分量据说是 1 到 3 个周期/字母 (cpl)，因此每个方向上的 6 个点应该足以表示一个字符；然而，一些研究表明，高密度字符更清晰。考虑到这些看似矛盾的发现可能是兼容的，我们分析了调整样本密度的角色刺激的频率成分，发现高密度角色中1至3 cpl的成分含量增加。在以下三个心理物理实验中，高样本密度的角色往往具有较低的对比度阈值，无论是正常视力还是低视力。此外，根据 1 至 3 cpl 分量的幅度预测每个样本密度特征的对比度阈值。因此，虽然增加样本密度可以提高易读性，但增加高频本身并不重要。研究结果表明，通过添加高频分量来增强对识别字符很重要的频率分量有助于使字符更清晰。